The present technique relates to an image processing method, control program and image processing apparatus for embedding information into an image.
In order to prevent forgery, prevent illegal use or provide an added service, technologies have been developed for embedding information to a print image or digital data, for example. The embedding information is not recognized by human eyes. An image containing the information may be used for claiming a right or for user interface, for example. The technologies allow information such as the name of a copyright holder and copy histories to be embedded to a print image and thus can prevent information leaks and/or copying. Encoded information may be embedded to a print image. Then, the code is obtained from the image with an input device such as a camera provided in a mobile information terminal to access the Internet.
One method for embedding a code to an image may divide an image into a predetermined number of blocks and changes the characteristic value of a subject block based on the characteristic amount of the image in a predetermined area of the subject block and information to be embedded. This method requires the division of an image into a predetermined number of blocks in order to allow decoding with an input device.
Here, in order to embed a code into a small image, the size of each block must be reduced since the number of blocks to be divided is predetermined. On the other hand, an input device has a characteristic called aperture indicating the pixel resolution. The size of the aperture depends on the input device and the distance from the input device to a subject to be imaged. For that reason, in a case that a code is embedded into a small image, other areas than the area containing the code are also read out for decoding due to the reading limit of the input device. As a result, information cannot be read out correctly.
Technique of the related art is disclosed in Japanese Laid-open Patent Publication No. 2004-349879.